Non-Response Errors

A non-response error is a non-sampling error that occurs when the investigator is unable to obtain information from a unit that was actually selected in the sample. This can happen in two ways: the interviewer may be unable to contact a person listed in the sample, or a selected person may refuse to respond.

When selected units drop out in this manner, the observations that are finally collected may fail to be representative of the population, because the people who could not be reached, or who declined to answer, might differ in important respects from those who did respond. As a result, conclusions drawn from the responding units alone can be misleading. Like other non-sampling errors, non-response cannot be removed merely by enlarging the sample; even a Census can suffer from it. Careful survey planning — repeated attempts to contact selected respondents, w …